2b22a6909d
Closes #325 Add a new subid_init() function which can be used to specify the stream on which error messages should be printed. (If you want to get fancy you can redirect that to memory :) If subid_init() is not called, use stderr. If NULL is passed, then /dev/null will be used. This patch also fixes up the 'Prog', which previously had to be defined by any program linking against libsubid. Now, by default in libsubid it will show (subid). Once subid_init() is called, it will use the first variable passed to subid_init(). Signed-off-by: Serge Hallyn <serge@hallyn.com>
499 lines
14 KiB
C
499 lines
14 KiB
C
/*
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* Copyright (c) 1991 - 1994, Julianne Frances Haugh
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* Copyright (c) 2008 - 2011, Nicolas François
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* Copyright (c) 2014, Red Hat, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the copyright holders or contributors may not be used to
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* endorse or promote products derived from this software without
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* specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <config.h>
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#include <assert.h>
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#include <stdio.h>
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#include <errno.h>
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#include "prototypes.h"
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#include "pwio.h"
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#include "getdef.h"
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/*
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* get_ranges - Get the minimum and maximum ID ranges for the search
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*
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* This function will return the minimum and maximum ranges for IDs
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*
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* 0: The function completed successfully
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* EINVAL: The provided ranges are impossible (such as maximum < minimum)
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*
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* preferred_min: The special-case minimum value for a specifically-
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* requested ID, which may be lower than the standard min_id
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*/
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static int get_ranges (bool sys_user, uid_t *min_id, uid_t *max_id,
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uid_t *preferred_min)
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{
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uid_t uid_def_max = 0;
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if (sys_user) {
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/* System users */
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/* A requested ID is allowed to be below the autoselect range */
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*preferred_min = (uid_t) 1;
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/* Get the minimum ID range from login.defs or default to 101 */
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*min_id = (uid_t) getdef_ulong ("SYS_UID_MIN", 101UL);
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/*
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* If SYS_UID_MAX is unspecified, we should assume it to be one
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* less than the UID_MIN (which is reserved for non-system accounts)
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*/
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uid_def_max = (uid_t) getdef_ulong ("UID_MIN", 1000UL) - 1;
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*max_id = (uid_t) getdef_ulong ("SYS_UID_MAX",
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(unsigned long) uid_def_max);
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/* Check that the ranges make sense */
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if (*max_id < *min_id) {
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(void) fprintf (shadow_logfd,
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_("%s: Invalid configuration: SYS_UID_MIN (%lu), "
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"UID_MIN (%lu), SYS_UID_MAX (%lu)\n"),
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Prog, (unsigned long) *min_id,
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getdef_ulong ("UID_MIN", 1000UL),
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(unsigned long) *max_id);
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return EINVAL;
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}
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} else {
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/* Non-system users */
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/* Get the values from login.defs or use reasonable defaults */
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*min_id = (uid_t) getdef_ulong ("UID_MIN", 1000UL);
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*max_id = (uid_t) getdef_ulong ("UID_MAX", 60000UL);
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/*
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* The preferred minimum should match the standard ID minimum
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* for non-system users.
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*/
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*preferred_min = *min_id;
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/* Check that the ranges make sense */
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if (*max_id < *min_id) {
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(void) fprintf (shadow_logfd,
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_("%s: Invalid configuration: UID_MIN (%lu), "
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"UID_MAX (%lu)\n"),
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Prog, (unsigned long) *min_id,
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(unsigned long) *max_id);
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return EINVAL;
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}
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}
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return 0;
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}
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/*
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* check_uid - See if the requested UID is available
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*
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* On success, return 0
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* If the ID is in use, return EEXIST
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* If the ID is outside the range, return ERANGE
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* In other cases, return errno from getpwuid()
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*/
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static int check_uid(const uid_t uid,
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const uid_t uid_min,
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const uid_t uid_max,
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bool *used_uids)
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{
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/* First test that the preferred ID is in the range */
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if (uid < uid_min || uid > uid_max) {
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return ERANGE;
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}
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/*
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* Check whether we already detected this UID
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* using the pw_next() loop
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*/
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if (used_uids != NULL && used_uids[uid]) {
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return EEXIST;
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}
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/* Check if the UID exists according to NSS */
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errno = 0;
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if (prefix_getpwuid(uid) != NULL) {
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return EEXIST;
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} else {
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/* getpwuid() was NULL
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* we have to ignore errors as temporary
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* failures of remote user identity services
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* would completely block user/group creation
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*/
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}
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/* If we've made it here, the UID must be available */
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return 0;
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}
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/*
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* find_new_uid - Find a new unused UID.
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*
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* If successful, find_new_uid provides an unused user ID in the
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* [UID_MIN:UID_MAX] range.
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* This ID should be higher than all the used UID, but if not possible,
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* the lowest unused ID in the range will be returned.
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*
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* Return 0 on success, -1 if no unused UIDs are available.
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*/
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int find_new_uid(bool sys_user,
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uid_t *uid,
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/*@null@*/uid_t const *preferred_uid)
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{
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bool *used_uids;
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const struct passwd *pwd;
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uid_t uid_min, uid_max, preferred_min;
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uid_t id;
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uid_t lowest_found, highest_found;
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int result;
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int nospam = 0;
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assert (uid != NULL);
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/*
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* First, figure out what ID range is appropriate for
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* automatic assignment
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*/
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result = get_ranges (sys_user, &uid_min, &uid_max, &preferred_min);
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if (result == EINVAL) {
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return -1;
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}
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/* Check if the preferred UID is available */
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if (preferred_uid) {
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result = check_uid (*preferred_uid, preferred_min, uid_max, NULL);
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if (result == 0) {
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/*
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* Make sure the UID isn't queued for use already
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*/
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if (pw_locate_uid (*preferred_uid) == NULL) {
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*uid = *preferred_uid;
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return 0;
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}
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/*
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* pw_locate_uid() found the UID in an as-yet uncommitted
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* entry. We'll proceed below and auto-set an UID.
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*/
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} else if (result == EEXIST || result == ERANGE) {
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/*
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* Continue on below. At this time, we won't
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* treat these two cases differently.
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*/
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} else {
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/*
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* An unexpected error occurred. We should report
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* this and fail the user creation.
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* This differs from the automatic creation
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* behavior below, since if a specific UID was
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* requested and generated an error, the user is
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* more likely to want to stop and address the
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* issue.
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*/
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fprintf (shadow_logfd,
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_("%s: Encountered error attempting to use "
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"preferred UID: %s\n"),
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Prog, strerror (result));
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return -1;
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}
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}
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/*
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* Search the entire passwd file,
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* looking for the next unused value.
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*
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* We first check the local database with pw_rewind/pw_next to find
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* all local values that are in use.
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*
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* We then compare the next free value to all databases (local and
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* remote) and iterate until we find a free one. If there are free
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* values beyond the lowest (system users) or highest (non-system
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* users), we will prefer those and avoid potentially reclaiming a
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* deleted user (which can be a security issue, since it may grant
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* access to files belonging to that former user).
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*
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* If there are no UIDs available at the end of the search, we will
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* have no choice but to iterate through the range looking for gaps.
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*
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*/
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/* Create an array to hold all of the discovered UIDs */
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used_uids = malloc (sizeof (bool) * (uid_max +1));
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if (NULL == used_uids) {
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fprintf (shadow_logfd,
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_("%s: failed to allocate memory: %s\n"),
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Prog, strerror (errno));
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return -1;
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}
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memset (used_uids, false, sizeof (bool) * (uid_max + 1));
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/* First look for the lowest and highest value in the local database */
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(void) pw_rewind ();
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highest_found = uid_min;
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lowest_found = uid_max;
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while ((pwd = pw_next ()) != NULL) {
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/*
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* Does this entry have a lower UID than the lowest we've found
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* so far?
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*/
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if ((pwd->pw_uid <= lowest_found) && (pwd->pw_uid >= uid_min)) {
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lowest_found = pwd->pw_uid - 1;
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}
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/*
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* Does this entry have a higher UID than the highest we've found
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* so far?
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*/
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if ((pwd->pw_uid >= highest_found) && (pwd->pw_uid <= uid_max)) {
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highest_found = pwd->pw_uid + 1;
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}
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/* create index of used UIDs */
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if (pwd->pw_uid >= uid_min
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&& pwd->pw_uid <= uid_max) {
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used_uids[pwd->pw_uid] = true;
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}
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}
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if (sys_user) {
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/*
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* For system users, we want to start from the
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* top of the range and work downwards.
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*/
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/*
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* At the conclusion of the pw_next() search, we will either
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* have a presumed-free UID or we will be at UID_MIN - 1.
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*/
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if (lowest_found < uid_min) {
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/*
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* In this case, an UID is in use at UID_MIN.
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*
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* We will reset the search to UID_MAX and proceed down
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* through all the UIDs (skipping those we detected with
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* used_uids) for a free one. It is a known issue that
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* this may result in reusing a previously-deleted UID,
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* so administrators should be instructed to use this
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* auto-detection with care (and prefer to assign UIDs
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* explicitly).
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*/
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lowest_found = uid_max;
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}
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/* Search through all of the IDs in the range */
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for (id = lowest_found; id >= uid_min; id--) {
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result = check_uid (id, uid_min, uid_max, used_uids);
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if (result == 0) {
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/* This UID is available. Return it. */
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*uid = id;
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free (used_uids);
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return 0;
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} else if (result == EEXIST) {
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/* This UID is in use, we'll continue to the next */
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (shadow_logfd,
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_("%s: Can't get unique system UID (%s). "
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"Suppressing additional messages.\n"),
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Prog, strerror (result));
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SYSLOG ((LOG_ERR,
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"Error checking available UIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later UID
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* will work properly.
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*/
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}
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}
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/*
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* If we get all the way through the loop, try again from UID_MAX,
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* unless that was where we previously started. (NOTE: the worst-case
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* scenario here is that we will run through (UID_MAX - UID_MIN - 1)
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* cycles *again* if we fall into this case with lowest_found as
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* UID_MAX - 1, all users in the range in use and maintained by
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* network services such as LDAP.)
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*/
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if (lowest_found != uid_max) {
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for (id = uid_max; id >= uid_min; id--) {
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result = check_uid (id, uid_min, uid_max, used_uids);
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if (result == 0) {
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/* This UID is available. Return it. */
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*uid = id;
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free (used_uids);
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return 0;
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} else if (result == EEXIST) {
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/* This UID is in use, we'll continue to the next */
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (shadow_logfd,
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_("%s: Can't get unique system UID (%s). "
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"Suppressing additional messages.\n"),
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Prog, strerror (result));
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SYSLOG((LOG_ERR,
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"Error checking available UIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later UID
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* will work properly.
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*/
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}
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}
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}
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} else { /* !sys_user */
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/*
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* For non-system users, we want to start from the
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* bottom of the range and work upwards.
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*/
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/*
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* At the conclusion of the pw_next() search, we will either
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* have a presumed-free UID or we will be at UID_MAX + 1.
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*/
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if (highest_found > uid_max) {
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/*
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* In this case, a UID is in use at UID_MAX.
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*
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* We will reset the search to UID_MIN and proceed up
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* through all the UIDs (skipping those we detected with
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* used_uids) for a free one. It is a known issue that
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* this may result in reusing a previously-deleted UID,
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* so administrators should be instructed to use this
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* auto-detection with care (and prefer to assign UIDs
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* explicitly).
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*/
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highest_found = uid_min;
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}
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/* Search through all of the IDs in the range */
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for (id = highest_found; id <= uid_max; id++) {
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result = check_uid (id, uid_min, uid_max, used_uids);
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if (result == 0) {
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/* This UID is available. Return it. */
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*uid = id;
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free (used_uids);
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return 0;
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} else if (result == EEXIST) {
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/* This UID is in use, we'll continue to the next */
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (shadow_logfd,
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_("%s: Can't get unique UID (%s). "
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"Suppressing additional messages.\n"),
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Prog, strerror (result));
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SYSLOG ((LOG_ERR,
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"Error checking available UIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later UID
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* will work properly.
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*/
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}
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}
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/*
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* If we get all the way through the loop, try again from UID_MIN,
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* unless that was where we previously started. (NOTE: the worst-case
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* scenario here is that we will run through (UID_MAX - UID_MIN - 1)
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* cycles *again* if we fall into this case with highest_found as
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* UID_MIN + 1, all users in the range in use and maintained by
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* network services such as LDAP.)
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*/
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if (highest_found != uid_min) {
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for (id = uid_min; id <= uid_max; id++) {
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result = check_uid (id, uid_min, uid_max, used_uids);
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if (result == 0) {
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/* This UID is available. Return it. */
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*uid = id;
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free (used_uids);
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return 0;
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} else if (result == EEXIST) {
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/* This UID is in use, we'll continue to the next */
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} else {
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/*
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* An unexpected error occurred.
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*
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* Only report it the first time to avoid spamming
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* the logs
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*
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*/
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if (!nospam) {
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fprintf (shadow_logfd,
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_("%s: Can't get unique UID (%s). "
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"Suppressing additional messages.\n"),
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Prog, strerror (result));
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SYSLOG ((LOG_ERR,
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"Error checking available UIDs: %s",
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strerror (result)));
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nospam = 1;
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}
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/*
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* We will continue anyway. Hopefully a later UID
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* will work properly.
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*/
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}
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}
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}
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}
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/* The code reached here and found no available IDs in the range */
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fprintf (shadow_logfd,
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_("%s: Can't get unique UID (no more available UIDs)\n"),
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Prog);
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SYSLOG ((LOG_WARN, "no more available UIDs on the system"));
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free (used_uids);
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return -1;
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}
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